[vsnet-grb-info 7208] GRB 081231: Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8781
SUBJECT: GRB 081231: Fermi GBM Detection
DATE:    09/01/06 02:43:13 GMT
FROM:    Adam Goldstein at Fermi-GBM/UAH  <adam.m.goldstein at msfc.nasa.gov>

A. Goldstein (UAH) and R. Preece (UAH) 
report on behalf of the Fermi GBM Team: 

"At 03:21:01.93 UT on 31 December 2008, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 081231 (trigger 252386462 / 081231140).

The on-ground calculated location, using the GBM trigger 
data, is RA = 218.74, DEC = -38.72 (J2000 degrees, 
equivalent to 14 h 35 m, -38 d 43'), with an uncertainty 
of 1.0 degree (radius, 1-sigma containment, 
statistical only; there is additionally a systematic
error which is currently estimated to be 2 to 3 degrees).
The angle from the Fermi LAT boresight is 20 degrees.
This burst was also independently detected by INTEGRAL SPI-ACS.

The GBM light curve consists of three main emission peaks with
apparent substructure and a duration (T90) of about 29 s (8-1000 keV). 
The time-averaged spectrum from T0-4.1 s to T0+37.9 s is best fit by
a Band function with Epeak = 152.3 +/- 11.9 keV, 
alpha = -0.80 +/- 0.06, and beta = -2.03 +/- 0.07. 
(chi squared 998 for 726 d.o.f.).

The event fluence (8-1000 keV) in this time interval is 
1.2E-05 +/- 5.9E-07 erg/cm^2. The peak photon flux measured 
starting from T0-4.1 s in the 8-1000 keV band 
is 1.53 +/- 0.08 ph/s/cm^2. 

The spectral analysis results presented above are preliminary; 
final results will be published in the GBM GRB Catalog."